Safety shutter for motion picture projectors



May 7, 1935- M. G. BLANK 2,000,575 n SAFETY SHUTTER FOR MOTION PICTUREPROJECTORS Filed March 28, 1933 2 Sheets-Sheet l amg May 7, 1935.

M. G. BLANK SAFETY SHUTTER FOR MOTION PICTURE PROJECTORS Filed March 28,1953 2 Sheets-Sheet 2 Passend May 7, i935P UNITED `STATES PATENT oFFicEThis invention relates to the motion pictureiI art and particularly tosafety shutters for motion picture projectors. One object of myinvention is to provide a motion picture projector I with a safetyshutter which is"pivoted tothe machine in such al manner that itnormallylies out of the path of a light beam passing through the illmbut is forced into thepath of the light beam as the speed of the machineis diminished* safety shutter which is counter-balanced in suchA amanner that it will normally move from its operative position lying in alightsbeam to anV inoperative position in which it lies outside of thelight beam, said shutter being counter-,balel anced in such a way thatonly a very slightforce is requiredto move the shutter into itsoperative position and other objects will appear from the followingspecification, the novel features being particularly pointed out intheclaims at theI end thereof. c i A Coming now to the drawings whereinlike reference characters denote like parts throughout;

Fig. l is a side elevation of a projector equipped with a safety shutterconstructed in accordance with and embodying a preferred form of myinvention;

Hg. 2 is a front elevation showing the shutter :gg safety shutterremoved from the projector;

Fig. 3 is a section on line 0 0 of Fig. 2.

As indicated in Fig. l a typical forml of projector may comprise a baseIfrom which abody portion 2 extends upwardly, this body portionsupporting the usual power drivensprockets I, objective I, gate i. l,pulldown c law l and lamp housel. A lamp l is positionedinthis lamphouse, being seated in a socket I0 so that' light rays from the illamentil may be projected in a' beam by means of thfe condenser system I2through a fl1m1F lying in the gate 5, 0 so that an image carriedby thefilm may be projected by the objective l on a screen in the usual manneralong the axis A oi' the light beam. It is customary to have a filmsupply l2 on a reel Il carriedbythesupportingarmllandthetllmistakeriupuponasecondreel Ilcarriedbytheariaa I6. It is understood thatthe mechanism for operatingthe movable parts are all included in thehousing 2.

Coming now to my invention the projector is 4 provided with theusuartype or shutter l1 and in 5 front'of this shutter there is a safetyshutter il, both shutters being adapted to cross the axis A of nthelight beam.

"Referring to Fig.`2 the usual projector shutter I1 may consist of asingle blade, as shown in this 10 figure, preferably counter-balanced ati9 and being adapted to interrupt the light beam three times for eachpicture frame although this is not essential to my invention. Theshutter i1 is i' carried by a shaft 20 which is rotated by power andwhich shaft lalso carries a governor which consists of a pair ofweighted levers 2| pivotally attached in a slot 22 in the end of theshaft upon a pin 23. The weights 24 of these levers are attached to theends of the levers so that as the shaft 2li is rotated centrifugal forcethrows these levers in the'direction shown by the arrows in F18- 3; yEach lever is provided with an arm 25 adapted to press bn a flat annularface 28 which is carried by a tubular slide 21 adapted to slide on thesleeve 2l pinned to the shaft 20. The flat face 28 is thrust towards thearms 2B by means of a spring 20 which also engages a collar 00 on theend of the tubular member 20.

There is an annular cam surface Il extending away from the at surface 26and this cam surface moves axially of the shaft 20v in accordance withthe position of the weighted arms 2|.

The safety shutter -I8 may consist of a medium forreducing heat rayssuch as a copper or other heat-dissipating wire screen, gold platedglass or mica, slotted metal or any other well known hea'tl `retardingmaterial. The materialsl above mentioned are adapted to pass certainlight rays for 0 projecting stills. It is obvious that if desired an,opaque screeny can be mounted inthe frame $3 which holds whatever heatretarding material isi desiredontheendofanarmll. Thisarmis pivotallymounted on the stud 8l and has a weighted end I0. .f

The weighted end Il is so arranged that it does not quitecounter-balance the weight of the A safety shutter I8. Consequently, thescreen normany tends to tum 'in the direction shown by 5 the arrow aboutthe pivot 35 mitil the arm [I strikes the lug Il which deilnes aninoperative position of the safety shutter il. The axis of the lightbeam is indicated in Fig. 2 as being the y point a. j y 1 55 operativeposition, as shown in Fig. 2, in which it crosses the axis A of thelight beam by turningY in Fig. 2. However, as soon as the speed'of thegovernor is reduced by the projector slowing up to a predeterminedamount the cam surfaces 3| and 38 contact and the screen is cammed andturns on its pivot 35 until the safety shutter I8 reaches its operativeposition with respect to the light beam axis A shown in full lines inFig. 2..

This position'will be retained as the projector continues to slow up andwhen the projector has been turned off the spring 29 continues to thrustthe weighted members 2| towards each other and continues to cause thecam surfaces 3| and 38 to contact, as shown best in Fig. 3.

With a safety shutter madein accordance with the preferred embodiment ofmy invention described above it will be seen that there are a. number ofadvantages which reduce the wear on the various parts which operate thesafety shutter and which lead to quiet and efficient operation.

Since the cam surfaces Il and 38 only contact when the projector isoperating below a definite speed during the greater portion of time thatthe projector is working there is no connection between the safetyshutter and its operating governor at all. 1

With the normal projection machine it only requires a very few secondsfor the machine to reach its operating speed. Consequently, there isvery little contact between the camY surfaces 3| yand 38 which has the'advantage of causing but little wear between these parts and also hasthe advantage of being quiet in operation, and allowing the weightedlevers 2| free play to gov- `ern the speed of the machine after it hasreached cam 3| takes place gradually as the weights 2l approach eachother there is a complete lack of the usual shock or blow which may becaused by parts rapidly coming in contact with each other.

What I claim as new and desire to. secure by Letters Patent of theUnited States is:

. 2,000,575 In order .to move the safety shutter I8 to itsv mountedsafety shutter, a weight attached thereto to incompletelycounter-balance the shutter whereby it normally moves on its pivot to aninoperative position, a governor mounted on a power driven shaft, saidgovernorA comprisingweighted levers pivoted to said shaft, a cam discmounted to slide axially of said shaft, a spring tending to move saidcam disc in one direction said weighted levers being adapted to movesaid 'cam disc in an opposite direction whereby said cam may contactwith said safety shutter only as the speed of the power driven shaftdecreases and said cam disc may then be moved by the spring intoposition to engage and move the safety shutter.

2. In a motion picture projector, the combination with a projectorshutter, a power driven shaft formoving said shutter, a safety shutter,a lpivotal support for said safety shutter, a speed governor on saidshutter shaft including an element adapted to move axially on saidshaft, a centrifugal control for moving the said' slidable element, saidslidable element being adapted to cooperate with the safety shutter andthrough engagement therewith to move the safety shutter. said slidableelement and safety shutter being so positioned relative to each otherthat contact between them will occur only at predetermined speeds ofsaid shaft.

3. In a motion picture projector, the combination with a shutter, of apower driven shaft for supporting said shutter, a governor carried bysaid shaft including a beveled disc slidably supported relative to saidshaft, a centrifugal control for said beveled disc, a safety shutterrmovably mounted on said projector and adapted to nor-v mally move to aninoperative position in which it is out of contact with the beveleddisc, a part of said safety shutter lying in the path of movement ofsaid beveled disc whereby said safety shutter may be moved to anoperative position through movement of said beveled disc in whichposition the safety shutter contacts with said beveled disc.

4. In a motion picture projector, the combina-v tion with a shutter, ofa power driven shaft for supporting said shutter, a governor carried bysaid shaft including a beveled disc slidably supported relative to saidshaft, a centrifugal control i'or said beveled disc, a spring for movingthe disc in -one direction, a safety shutter movably mounted on saidprojector and adapted to normally move to an inoperative position inwhich it is out of contact with the beveled disc, a part 4 L'A safetyshutter for motion picture proiectors"including in combination, apivotallyl

